1. Field of the Invention
This invention relates to a golf ball comprising a core, an intermediate layer, and a cover. More particularly, it relates to such a golf ball in which a resilient intermediate layer is formed of an easily moldable resin component consisting essentially of a mixture of a thermoplastic elastomer and an ionomer resin so that the ball may have excellent flight performance and pleasant hitting feel as well as improved durability against hitting.
2. Prior Art
Golf balls of various structures are on the market. Among others, two-piece solid golf balls having a rubber base core enclosed with a cover of ionomer resin or the like and thread-wound golf balls comprising a wound core having thread rubber wound around a solid or liquid center and a cover enclosing the core share the majority of the market.
Most amateur golfers are fond of two-piece solid golf balls which have excellent flying performance and durability although these balls have the disadvantages of a hard feel on hitting and low control due to quick separation from the club head on hitting. For this reason, many professional golfers and low handicap amateur golfers prefer wound golf balls to two-piece solid golf balls. The wound golf balls are superior in feeling and control, but inferior in flight distance and durability to the two-piece solid golf balls.
Under the present situation that two-piece solid golf balls and wound golf balls have contradictory characteristics as mentioned above, players make a choice of golf balls depending on their own skill and preference.
Various attempts have been made to solve the above-mentioned problems. One attempt is to interpose a resin layer or intermediate layer between the core and the cover to impart various properties. For example, U.S. Pat. No. 4,431,193 discloses a golf ball comprising a core, an intermediate layer formed of a hard, high flexural modulus ionomer resin, and a cover formed of a soft, low flexural modulus ionomer resin. The intermediate layer of hard resilient ionomer resin compensates for a loss of resilience inherent to the use of a soft cover. The golf ball of this patent, however, has the problems of a hard hitting feel and substantially deteriorated durability against repetitive hitting because a very hard, high or moderate acid content ionomer resin is used as the intermediate layer.
As one solution, U.S. Pat. No. 4,884,814 proposes to reduce the hardness of an ionomer resin in the intermediate layer. The golf ball of this patent, however, is low in restitution and fails to provide satisfactory flight performance.
None of the golf balls having an intermediate layer between the core and the cover have reached a fully satisfactory level. There is a need for further improvement and development.
Therefore, an object of the present invention is to provide a golf ball comprising a core, an intermediate layer and a cover in which an easily moldable, highly resilient material is used as the intermediate layer so as to improve the adhesion of the intermediate layer to both the core and the cover and improve the flight performance, hitting durability, and hitting feel of the ball.